Guide for grinding devices



- 3 M. P. SCHMIYTT GUIDE FOR GRINDING DEVICES --Filed N0 v. 3, 1921.

. INVENTOR M Pficimz if.

Patented duly 1?, 1923.

mrsn STATES PATENT QFFMZE.

MICHAEL P. SCHMITT, or NORTH CHICAGO, rnmivois,

GUIDE FOR GRINDING DEVICES.

Application filed November 3, 1921. serial No. 512,449.

dent of North Chicago, in the county of Lake and State of Illinois, haveinvented;

- My invention relates to guides for grinding devices, and moreparticularly to that type of grinding device used for the sharpening oflawn mower blades and the like.

An object of my invention is to provide a guide for grinding device inwhich the depth of the out about to made may be accurately determined.

A further object of my invention is to provide a guide for grindingdevice in which variation in the grinding of a straight blade due to theelastic properties of the grinding wheel support is reduced to aminimum-Other objects and advantages will appear in the following specification,and the novel features of the invention will beparticularly pointed outin the appended claim.

My invention is illustrated in the accompanying drawings, forming partofthis ap plication, in which Fig. 1 is a perspective view of anembodiment of my invention, 1 i

Fig. 2 is a sectional view along the line 22 of Fig. 1, and

Figure 3 is a partial sectional view of a part of the mechanismillustrated in Figure 1.

In carrying out my invention, 1 make use of the ordinary type of lawnmower grinding device, such as is illustrated in Fig. 1, the sub-base ofwhich is shown broken away. This grinding device consists in a centralshaft 1 rotatably supported upon the frame 2. Means for connecting theshaft to a driving mechanism is provided in a pulley wheel 3 mounted atone end of the shaft. A. grinding wheel 1 is rotatably supported upon alever member 5 having for its fulcrum the shaft 1. The grinding wheel 4is operatively connected by means of a chain 6 to a sprocket wheel 7.The sprocket wheel 7 is feathered upon the shaft 1 so that it may bedriven thereby and thus in turn drive the grinding wheel 4. The levermember 5 is free to travel, carrying with it the sprocket 7 upon theshaft 1. j

Automatic means for feeding the lever carrying the grinding wheel 4 fromone end in parallel relation with the shaft 1.

ofthe shaftl to theother end is provided in a threaded feed shaft 8which is placed 1 Since the shaftl revolves at a considerable speed, itis necessary to provide a reduction gear mechanism intermediate theshaft1 and the feed shaft 8. In this case, the reduction mechanism comprisesa large sprocket wheel 9 which is operatively connected by means of achain 10to a relatively small sprocket wheel 11 carried by the. shaft 1.The sprocket wheel 9 is operatively connected to drive the feed shaft 8.Asupporting shaft 12 is disposed parallel and closely adjacent the feedshaft 8 substantially as shown in Fig. 2. r i

A downwardly extending bracket member 13 is slidably disposed upon thesupporting shaft 12. The bracket 13 is provided with a rearwardextending threaded sleeve portion 14, the threads of which are in meshwith the threads upon the feed shaft 8. The lever member 5 is movablyengaged with the bracket 13 so that movement 'or the bracket 13 alongthe supporting bar12 will carry the lever member 5 and the grindingwheel with it. The bracket 13 is also provided with adjustable means forlimiting the downward movement of that portion of the lever 5 carryingthe grinding wheel 1, the purpose of which will hereinafter bedescribed.

A finger member 15 is supported upon the lever 5 at the outer endthereof and carries an adjustable hook 16 which may be extended or drawninto the casing of the finger 15. The finger 15 may also be'turned atvarious angles with respect to the lever 5 upon its fulcrum 17. Astraight edge 18 consisting of a steel angle iron, one surface 19 ofwhichhas been ground to a true straight edge is movably supported upon across frame 20 of the frame 2 by means of adjustable clamping members21.

From the foregoing description of the various parts of the device, theoperation thereof may be readily understood. The

practice in the past of grinding a straight ing shaft 12 andthe feedshattS both are apt to give slightly from the weight of the grindingwheel/l as it approaches the-central points of these shafts. Also,chattering ot the grinding wheel 4 upon the blade'2 is likely to throwthelever 5 up slightlyand in coming down'it strikes the flanged clamp insuch. a way as to cause a slightchange in position of the clamp. Becauseof the 'leverage present in the relation of the wei ht of the grindingwheel '4 and the position of the bracket 13 almost any undue pressure orvibration of the wheel willbe likely to cause a strain on the shafts 8and 12 to bring about a variation in the blade when ground. r i

This means of guidingthegrinding wheel 4: relative to the blade22and'its disadvantages are done away within the present invention. Thestraight edge 18 is supported in substantially parallel relation withthe blade 22. The hook 16 of the finger is then adjusted so as to'restupon the surface 19 of the straight edge 18 in a manner to menseslimitthe downward movement of the grinding wheel 4. If the hook 16 isnow elevated until the grinding Wheel at strikes the blade 22, thedistance between the hook 16 and the surface 19 will be exactly thedepth of the cut to be made upon the blade.

It will be seen by employing the straight edge 18 there isabsolutely novariation in the relation between the grinding wheel 18 and the bladefrom the beginning of the out until the'fin'ish.

This guide for grinding wheel may be applied ,to any of the grindingmachines now in use without in anyway eitecting'the operation of themeans forgrinding the 'rota'ry blades of the lawn mower.

I claim: I The combination with a grinding machine having a power drivengrinding wheel, a

clamp for holding a straight blade transverse to said grinding wheel,and means 'for movingsaid grinding wheel from one end or said blade tothe other, of a rigid angle 7 bar having an accurately fashioned flatstir-' Face thereon, a pair of clampingine'mbers it'or adjustablysecuring said bar {to said machine adjacent and parallel to said blade,and an adjustable finger associated with the support for said grindingwheel, said-finger being adapted to rest (in-said flat sur face'to causesaid grinding wheel to be limited in itsengagementwith said bladeuniformly throughout the grinding operation.

MICHAEL P. SCHMITT,

